The present application claims priority to Japanese Application No. P2000-084747 filed Mar. 22, 2000, which application is incorporated herein by reference to the extent permitted by law.
The present invention relates to a battery electrode which exhibits good flexibility while keeping its performance. The present invention relates also to a non-aqueous electrolyte battery.
The recent years have seen the appearance of a variety of portable electronic machines and equipment such as VTR with integrated camera, portable telephones, and portable computers. Efforts are being made to make them smaller in size and lighter in weight and to improve their performance. Such improved performance also needs high-performance portable power sources, such as batteries, particularly secondary batteries, among which are lithium ion batteries attracting attention.
Such batteries are required to have good electrical properties as well as good shape. In other words, there is a demand for a battery of new type which is flexible and can be fitted into a movable or curved part of an electronic machine.
Conventional batteries, however, are constructed such that battery elements are placed in a metal can and hence they hardly change in shape. By contrast, sheet-like batteries that employ a gel electrolyte or solid electrolyte can change in shape to a certain extent, but they are not sufficiently flexible because they have metal current collectors forming a bridge.
The above-mentioned sheet-like batteries can be bent by force for their change in shape. Bending, however, causes the positive and negative electrodes to separate from each other at the bent part, breaks balance between the positive and negative electrodes, and causes the active material to separate from the current collector. All this greatly deteriorates the battery performance.
The present invention has been proposed to address these problems. It is an object of the present invention to provide a battery electrode which can bend arbitrarily without causing the active material to peel off. It is another object of the present invention to provide a non-aqueous electrolyte battery which can change in shape without deteriorating the battery performance.
To achieve the above object, according to a first aspect of the present invention, there is provided a battery electrode including a sheet-like metal current collector and a layer of active material formed thereon, wherein at least the metal current collector has cut lines so as to be flexible.
According to a second aspect of the present invention, there is provided a non-aqueous electrolyte battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode and/or negative electrode is constructed such that a layer of active material is formed on a sheet-like metal current collector and at least the metal current collector has cut lines so as to be flexible.
A non-aqueous electrolyte battery with a gel electrolyte employs a so-called bridge structure. In other words, it has the respective metal current collectors for the positive and negative electrodes placed one over the other with a gel electrolyte interposed between them to isolate stress.
The metal current collector can bend in itself; but it can hardly bend if used in bridge structure. The reason for this is the same as that a metal pipe cannot bend easily.
The battery electrode according to the present invention is easily flexible because the metal current collector has cut lines. Thus, the non-aqueous electrolyte battery can be easily bent even when it employs bridge structure.